1. Field of the Invention
The invention relates to an integrated optic waveguide and to the method for making it. In particular, it relates to a structure in which the waveguide is buried.
In the past few years, new organic materials with promising electronic properties have been developed. There are two distinct aspects to research and design work on to these materials: these are the designing of the material (improvement of the physical characteristics, chemical synthesis, etc.) and the designing of the optoelectronic components that use these materials.
The object of the invention lies within the context of the latter aspect. Making optoelectronic components that use these new materials means that it is necessary, first of all, to design the architecture of the component, and secondly to devise and perfect the entire technological process needed for the effective fabrication of the component.
The object of the invention, therefore, relates to electronic components using electrooptical organic polymers. The electrooptical organic materials used in the making of these components are optically non-linear materials. This optic non-linearity is generally capable of being used only after the materials have been deposited as thin films (by spin-coating as in microelectronics) and polarized under an electrical field. It is thus possible to make small-sized phase or intensity modulators having good optical characteristics.
However, the one-dimensional confinement of the light is not sufficient. The making of an optoelectronic component dicates a search for two-dimensional confinement. The mastering of this technology will lead to a new generation of very low-cost integrated optoelectronic components: phase or intensity modulators, electrooptical switches for telecommunications by optic fibers, frequency doublers (to obtain, for example, green or blue radiation) for the storage or reading of data.
2. Description of the Prior Art
A number of approaches have been developed, enabling two-dimensional confinement to be achieved.
A first approach shown in FIG. 1 consists in locally increasing the effective index encountered by the light by locally increasing the thickness of the polymer. However, it is extremely difficult to keep to the dimensions dictated by the architecture of the component, both transversally and in depth. Furthermore, although FIG. 1 shows a perfect planarization of the polymer, this is rarely the case owing to the depth of the etching.
A second approach, shown in FIG. 2, provides for a direct dry or chemical etching of the polymer 1 which raises the problem of the etching mask and the quality of the result obtained.
A third approach, shown in FIG. 3, provides for the deposition of a metal electrode on the polymer and then for the etching of this electrode. This raises problems of selectivity of etching and of possible chemical damage to the polymer.
A fourth approach, shown in FIG. 4, provides for confinement by local modification of the nature of the material, which can be done by UV insolation through a mask. This raises a problem of diffraction and of the creation of an index gradient by uncontrollable UV radiation.
Finally, a fifth approach shown in FIG. 5 provides for a modification of the assymmetry of a planar guide by local doping of a glass substrate. This approach raises a problem of the polishing of the guide input and output faces.